Overcloud CephStorage scale out failed with GRUB2 error

Issue

• Ceph node scale-out would fail on all new nodes with the following backtrace and results in overcloud deploy failed.

Oct 13 05:08:53 host-10-244-20-27 ironic-python-agent[3154]: 2022-10-13 05:08:53.125 3154 ERROR ironic_python_agent.extensions.image [-] Error setting up bootloader. Error Command execution failed: Installing GRUB2 boot loader to device /dev/sda failed with Unexpected error while running command.
                                                             Command: mount /dev/sda3 /tmp/tmp2wce2sw2
                                                             Exit code: 32
                                                             Stdout: ''
                                                             Stderr: 'mount: /tmp/tmp2wce2sw2: /dev/sda3 already mounted on